Update on AY-3-8910 schematic

The original schematics I provided for the Arduino + AY-3-8910 was a bit crude for the audio output, it works, but it’s easy to get the audio saturate. I will propose you an update on this, taken from an actual schematic, the one used on the Oric 1/Atmos

The Oric also use an AY-3-8910 as its sound chip, and I never heard the audio saturate in all conditions.

So first we should have a look at how the Oric mix the 3 channels from the PSG chip:

oric_audio
This schematic is of course much more complexe than what we need, as we don’t drive a keyboard, and we don’t need an amplifier like the Oric who used a standard HP. For normal headphone and externally amplified HP, something near a line-out is sufficient, and if you look at the schematic it’s exactly what the “SOUND_OUT” output port have, so we will need only a few passive component to give the output a better shape.

So we only need 3 resistors and 2 capacitors to give the output a better shape:oric_audio_detail

What is interesting in this schematic is that it is made from a low pass filter and a high pass filter.

I’ve made a breadboard schematics for those of you who want one:AY-3-8910_Arduino_bbI used chemical capacitor on the drawing, but you may not find chemical of that capacity, on the original schematic, C1(C5) is a ceramic capacitor, and C2(C4) is a tantalum one. But the most important information is the capacitance in farad, not the capacitor type, at least for this application.

I will try to update quite soon the repository of this project with this new schematic and a few bug fix on the software.

Enjoy playing music with you PSG chips 🙂

 

Edit 08/05/2015: I’ve update the Fritzing Schematics with the latest corrections 🙂